Sterigmatocystin, i.e., ST, as an aflatoxin intermediate, is the early-stage intermediate during the synthesis of aflatoxins. ST is mainly produced by fungi such as Aspergillus versicolor, Aspergillus flavus, Aspergillus nidulas, and Aspergillus rugulosus, etc., may contaminate most of grains and forage grasses, and in particular severely contaminate wheat, maize, peanut and forage grasses. The basic structure of aflatoxin biosynthesis precursor ST consists of a difuran ring in connection with xanthone. The precursor has a structure similar to that of aflatoxin, and has toxicity that is second only to that of aflatoxin. Toxicity of ST includes hepatotoxicity, nephrotoxicity, cytogenetic toxicity and strong carcinogenicity. It enters into the human food chain after contaminating foods, and feeds and poses a threat to the health and safety of human. The hazard degree has a positive correlation with the intake of aflatoxin biosynthesis precursor ST. Since China is an area where there is more severe contamination with aflatoxin biosynthesis precursor ST, one of the key points to fortify the food safety is to improve detection of aflatoxin biosynthesis precursor ST in food products and feeds. Accordingly, it is necessary to determine the content of ST in cereals and finished products thereof suspected to be contaminated with the aflatoxin biosynthesis precursor ST.
Currently, methods for detecting aflatoxin biosynthesis precursor ST mainly include thin-layer chromatography (TLC) and liquid chromatography. TLC is easy to operate, and does not require complex and precise instrumentation, but has low sensitivity and low accuracy. Using TLC, a lower limit of detection of aflatoxin biosynthesis precursor ST in rice, maize, and wheat samples is 25 μg/kg and that in soybean and peanut samples is 50 μg/kg. In the recent years, high-performance liquid chromatography (HPLC) has been used widely in the detection of fungal toxins and has also been reported for detecting the aflatoxin biosynthesis precursor ST. However, the application of the HPLC in detection at the basic level has been limited by tedious pre-processing, expensive instrumentation, requirements for stringent operation environment, and professional operators, etc. Therefore, there is a pressing need in the detection field in China to study and develop novel techniques for rapid detection of aflatoxin biosynthesis precursor ST, which is of importance on guaranteeing the safety in food consumption in China.
Immunological analysis techniques, which have been developed in recent years, have been increasingly the focus of rapid detection techniques for pollutants such as aflatoxin, due to advantages such as high sensitivity, short detection time, and easy to operate, etc. However, there are few reports on rapid detection techniques for aflatoxin biosynthesis precursor ST. Antigens and antibodies are the core reagents and the technological sources in immunological analysis techniques. The aflatoxin biosynthesis precursor ST has a molecular weight of 324, belongs to small molecule compounds (≦1000) and is incapable of directly stimulating an animal to produce antibodies. Only after covalently coupled to a carrier protein such as bovine serum protein (BSA), egg white albumin (OVA), and polylysine, etc., would aflatoxin be converted into an artificial antigen with both reactogenicity and immunogenicity which can stimulate an animal to produce antibodies. Currently, the artificial antigen of aflatoxin biosynthetic precursor ST is obtained mainly via preparation by sodium borohydride reduction, the sensitivity of the antibodies obtained using this artificial antigen is often not high.